A number of different approaches are being utilized to estimate the mortality and morbidity of Alzheimer's disease/senile dementia in several population groups in the U.S. and to measure the distribution of this disease in segments of the population. To study international variation in the epidemiology of Alzheimer's disease, a uniform protocol for definition of disease and methodology has been developed. This is now being applied in the U.S. in Denver, Colorado, and White Plains, N.Y., and in a multicenter study in Italy. There have been many requests to apply this protocol in many different parts of the world.